1. Field of the Invention
The present invention relates to an initial copy system for remotely copying data.
2. Description of the Related Art
Disaster recovery for protection of data in a storage system upon trouble and disaster is known as a backup technology.
Remote copy is used for the disaster recovery in which data is duplicated in a logical device in a storage system installed in a main site and the duplicated data is recorded in a logical device in another storage system installed at a remote site. More specifically, in remote copy, there is provided target volumes of a copy in a regular storage apparatus of a copy source and a sub-storage apparatus of a copy target. Then, the data in a regular logical device in the regular storage apparatus is continuously copied in a sub-logical device of the sub-storage apparatus so as to make the data in the regular logical device coincident with that in the sub-logical device in the sub-storage apparatus.
Use of the remote copy preferably provides data in storage apparatuses at respective places collected in the storage system in a data center in a real-time manner. Here, a pair of the regular logical device and the sub-logical device are referred to as a remote copy pair. Generation of the remote copy pair requires copying all data in the regular logical device into the sub-logical device. This operation is referred to as initial copy.
Conventionally, the initial copy was done by forwarding the data of a remote copy target in the regular storage system to the sub-storage system through a network. In this method, there is a problem that completion of the initial copy requires an extremely long duration if an amount of data of an initial copy target is large or a band of the network is small.
Japanese laid-open patent application publication No. 15-99309 (2003-99309) discloses the following methods to efficiently perform the initial copy.
In the first method, the regular storage apparatus and the sub-storage apparatus are located at the same site, and the initial copy is performed with a high speed network used for short distance communication, and then, the sub-storage apparatus is moved to a remote site after completion of the initial copy. In the second method, the data in the regular storage apparatus is copied in a recording medium (such as a magnetic recording tape), which is moved to the remote site where the data is copied from the recording medium in the sub-storage apparatus. In the third method, the data stored in one or more disk units (first disk unit group) in the regular storage apparatus is copied in another one or more disk units (second disk unit group), and then, the second disk unit group is removed from the regular storage apparatus and moved to a remote site to install the second disk unit group in a sub-storage unit.
Japanese laid-open patent application publication No. 10-283272 discloses technology in which to a first storage apparatus is connected a second storage apparatus, and if a device that is a target of a read/write request received by the first storage apparatus from a host computer has correspondence with the second storage apparatus, the read/write request is done by transmitting the read/write request from the first storage apparatus to the second storage apparatus.
Increase in need for disaster recovery may increase demands for collecting data such that data in logical devices in regular storage apparatuses arranged at a plurality of sites of an enterprise are duplicated by the remote copy in logical devices in a sub-storage apparatus arranged in a site (data center). However, the technology disclosed in Japanese laid-open patent application publication No. 15-99309 may show a problem that it is difficult to improve the efficiency in the initial copy for remote copying.